FLUORAPATITE-COATED IMPLANTS IN EXPERIMENTAL ARTHRITIS - THE RESPONSEOF RABBIT TRABECULAR BONE

Fluorapatite-coated implants have been studied for the first time unde r non-optimal tissue conditions and have shown promising results. The influence of arthritis on the tissue response to implants coated with fluorapatite (FA) was studied in an arthritis model. Immune complex-in duced arthritis was elicited in the right knee-joint of eight rabbits while the contralateral joint served as control. Ti-6Al-4V cylinders, plasma-spray coated with FA were implanted in the patellar groove (PG) and medial femoral condyle (MC) in each knee for 6 weeks. Histology s howed a close bone-to-implant contact at the lateral surface of the im plants without any intervening soft tissue or inflammatory cells. Hist omorphometry revealed no differences in bone apposition between contro l and arthritic joints, but the MC-implants showed more bone appositio n than the PG-implants. Parts of the implant surface were not covered by bone, but were in contact with bone marrow. The FA coating on the i mplant sides did not show signs of resorption in the control and arthr itic joints, but the coating on the upper surface of the implants was partially resorbed in both the control and arthritic joints. The arran gement and composition of the regenerating tissue in this location was profoundly influenced by the inflammatory process in the arthritic jo ints. In a previous study, using the same arthritis model, an impaired bone formation was found around commercially pure titanium implants i n arthritic joints. In the present study, the unimpaired bone formatio n around FA-implants in the arthritic joints indicates that an FA coat ing adds advantageous properties to metal implants used in tissues inf luenced by an on-going inflammation.